密文明文长度比可变的多变量公钥加密方案

多变量公钥密码体系是一种能保证后量子通信安全的重要方法。现今,能投入到实际应用、高效且安全的多变量公钥签名方案有很多,加密方案却很少。2013年后量子密码会议上,Tao等人提出了简单矩阵加密方案。该方案在保证安全性的前提下,具有较高的效率,但该方案的密文明文长度比固定为2。针对这一情况,对简单矩阵加密方案进行改进,提出Cubic AB加密方案。在该方案中,矩阵A的各元素由随机二次多项式构成;并选用一个扁长的矩阵来取代原方案中的B、C矩阵。使得该方案在能抵抗秩攻击的同时,密文明文长度比能灵活改变。并且随着安全性的提高,密文明文长度会相应减小,解密过程也随之加快。

Multivariate public key cryptography scheme with changeable ratio of ciphertext length to plaintext length

Multivariate public key cryptosystem is an important method to guarantee the security of communication after quantum computer appears. There are lots of practical multivariate signature schemes, but only a few multivariate encryption schemes show up. The simple matrix encryption scheme proposed by Tao, et al. is an efficient and secure multivariate encryption scheme in PQCrypto2013. However, the ratio of length of cipher text to plain text is always 2. Cubic AB encryption scheme is a way to fix it. It uses a very wide matrix to replace square matrixes (B and C), and the elements of matrix A are random quadratic polynomials. With this method, the ratio of length of cipher text to plain text could be changed easily. Besides, rank attack cannot be used to attack this scheme. At the same time, the length of cipher text and plain text will be shorter, which could make the process of decryption faster.